This invention relates to an ink mist type high speed printer.
Speed-up of the central processors in the electronic computer systems is necessitating corresponding speed-up of the printers which are output terminal units of such computer system. There are known various types of high speed printers, and among them is a so-called ink mist type high speed printer in which the ink mist particles electrically charged by ions are moved toward a printing paper to print desired characters by way of dot matrices on the printing paper. More particularly, according to such ink mist type printer, the ink mist particles in a stream of ink mist are selectively charged by cations which move from a second positive electrode to a first negative electrode in a back bar through an aperture board, and the electrically charged ink mist particles are carried by electrostatic force toward a recording paper placed between the stream of ink mist and back bar to thereby print characters by way of dot matrices on the recording paper.
The said type of high speed printer is usually so designed as to permit printing of 132 to 136 characters (letters, etc.) on each line. Therefore, when using a recording paper with a narrow printing space, no shield is present between the back bar and stream of ink mist in the area outside of the space of the printing paper. In such a case, if insulating dust such as flocks of the recording paper should contact the back bar which is a negative pole, such dust is charged negative and attracted toward the aperture board which is relatively high potential to the back bar. As such dust passes through the stream of ink mist, the dust particles carry the ink mist particles therewith, causing ink to adhere to the aperture board. Also, if such dust is loaded with ink to become insulating and deposits on the back bar, there takes place concentration of the electric field in the vicinity of said dust to cause discharge between the back bar and aperture board to anionize air in the neighborhood of said dust. These anions are also attracted to the aperture board, so that they pass through the laminar stream of ink mist to electrically charge the ink mist particles, causing deposition of ink on the aperture board.
Such deposition of ink on the aperture board leads to various troubles. For example, the cation outlet may be clogged, or the common electrode provided on the front side of the aperture board and the control electrodes provided on the back side thereof may be brought into a conductive state to retard the function of controlling passage of cations.